Clad board for printed-circuit board, multilayered printed-circuit board, and method of manufacture thereof

ABSTRACT

In the present invention, which produces a clad sheet for a multilayered printed circuit board capable of being economically manufactured and having excellent performance, a multilayered printed circuit board using thereof and a manufacturing method thereof, a multilayered printed circuit board is manufactured by 
     forming clad sheet for a multilayered printed circuit board  34  by 
     laminating copper foil  19, 24, 33  which are to be formed into conductor layer  10, 17, 18  and nickel plating  20, 21  which are to be etching-stopper layer and 
     simultaneously press-bonding both, 
     producing a base by selectively etching clad sheet for a multilayered printed circuit board  34,    
     forming outer conductor layer  15, 16  on the surface of the base and 
     simultaneously making patterning, and 
     electrically connecting among conductor layer  10, 15, 16  by 
     interposing columnar conductor  17, 18  formed by etching copper foil  19, 24, 33  and nickel plating  20, 21.

The present application is the national stage under 35 U.S.C. 371 ofPCT/JP99/03908, filed Jul. 22, 1999.

INDUSTRIAL FIELD

The present invention relates to a multilayered printed circuit boardapplicable to vast integration of semiconductor and a manufacturingmethod thereof.

BACKGROUND OF THE INVENTION

Currently, a highly integrated assembly board has been requiredaccompanied with the demands for higher integration, more pins and lowerweight of a semiconductor device. In order to accomplish these demands,research and development for multiplying the layers of a circuit boardand improving the circuit integration have been made.

As a method for multiplying the layers, a so-called building up methodhas been developed and is widely used. The method consists of laminatingan insulating layer and a circuit layer in which the connection betweenthese layers is accomplished by photoetching the insulating layer,forming via holes and then forming a plating layer on the surface. Insome cases, a laser is used for forming the via holes.

Japanese laid open publication No. Hei 8-264971 discloses amanufacturing method of a multilayered printed circuit board using abuilding up method. The manufacturing method of this application issimply explained referring FIG. 9 as mentioned below.

At first, the first resin layer 53 is formed in range 52 where anypattern is not formed on internal board 51 having internal conductorpattern 50. The first resin layer 53 is formed so that prescribedclearance 54 is made between the lateral of internal conductor pattern50 and the first resin layer 53. Next, the second resin layer 55composing an insulating layer by coating and then hardening resinvarnish. The second resin layer 55 fills up clearance 54 and coversinternal conductor pattern 50 and the first resin layer 53. Then,adhesive layer 56 is formed on the second resin layer 55 followed byroughening. After that, outer conductor pattern 57 is formed on adhesivelayer 56 be electroless plating.

However, the above-mentioned multilayered printed circuit board bybuilding up method has the following problems to be solved.

Namely, in the above-mentioned method, when a multilayered printedcircuit board is manufactured by laminating outer conductor pattern 57on both sides of internal board having internal conductor pattern 50,complicated processes such as formation of the first resin layer 53,formation of the second resin layer 55 by coating and then hardeningresin varnish, and further formation of adhesive layer 56 are required.For this reason, the reduction of cost of a multilayered printed circuitboard using the building up method could not be attained.

There is another manufacturing method of multilayered printed circuitboard in which metal thin film is formed by vaporizing.

However, the method has a problem that when the film is thin (a few μm),pores are easily caused, while when the film is thick (10 μm or more),the productability is deteriorated, which causes high cost.

The present invention aims to solve such problems. The objective of thepresent invention is to produce a clad sheet for printed circuit boardwhich can be manufactured at low cost and has excellent properties, amultilayered printed circuit board using thereof and a manufacturingmethod thereof.

DISCLOSURE OF THE INVENTION

The clad sheet for printed circuit board according to the presentinvention is characterized in that it is manufactured by press-bonding acopper foil and a nickel foil at a reduction rate of 0.1 to 3%.

The clad sheet for printed circuit board according to another embodimentis characterized in that it is manufactured by press-bonding a copperfoil of which one side or both sides have nickel plating layer andanother copper foil or a copper foil of which one side has nickelplating layer.

The clad sheet for printed circuit board according to another embodimentis characterize in that it is a five-layered sheet comprising layers ofcopper/nickel/copper/nickel/copper.

The multilayered printed circuit board according to another embodimentis characterized in that it comprises:

a base having an internal conductor layer formed by selectively etchingthe clad sheet for printed circuit board as described above,

an insulating layer and an outer conductor layer formed on the surfaceof said base,

said outer conductor layer being made patterning, and

the internal conductor layer and the outer conductor layer beingelectrically connected by interposing a columnar conductor formed insaid base by etching.

The manufacturing method of a multilayered printed circuit boardaccording to the present invention is characterized in that it iscomprising:

forming a clad sheet for printed circuit board by laminating a copperfoil serving as a conductor layer and a nickel foil or nickel platingserving as an etching-stopper layer and by simultaneously press-bondingboth at the reduction raze of 0.1 to 3%,

producing a base by selectively etching said multilayered clad street,

forming an insulating layer and an outer conductor layer or the surfaceof said tease,

making patterning said outer conductor layer, and

electrically connecting the internal conductor layer end the outerconductor layer by interposing a columnar conductor formed in said teaseby etching.

The manufacturing method according to another embodiment ischaracterized in that:

said clad sheet for printed circuit board is formed by laminating saidcopper foil and said nickel foil or nickel plating andcold-press-bonding both at the reduction rate of 0.1 to 3% aftercontacting surfaces or said copper foil and said nickel foil or nickelplating are previously activation-treated in a vacuum chamber, and inthat case,

said activation treatment is carried out

(1) in a hyper low pressure inert gas atmosphere of 1×10⁻¹ to 1×10⁻⁴Torr,

(2) by glow-discharging charging alternate current of 1 to 50 MHzbetween an electrode A consisting of said copper foil and said nickelplating having contacting surface which are electrically groundedrespectively end other electrode B insulatingly held, and

(3) by sputter-etching

(4) in the manner that the area of the electrode exposed in plasmagenerated by said glow-discharging is no more than ⅓ the area ofelectrode B.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 is a process explanatory view of an embodiment of themanufacturing method of the multilayered printed circuit board of thepresent invention

FIG. 2 is a process explanatory view of an embodiment of themanufacturing method of the multilayered printed circuit board of thepresent invention

FIG. 3 is a process explanatory view of an embodiment of themanufacturing method of the multilayered printed circuit board of thepresent invention

FIG. 4 is a process explanatory view of an embodiment of themanufacturing method of the multilayered printed circuit board of thepresent invention

FIG. 5 is a process explanatory view of an embodiment of themanufacturing method of the multilayered printed circuit board of thepresent invention

FIG. 6 is a process explanatory view of an embodiment of themanufacturing method of the multilayered printed circuit board of thepresent invention

FIG. 7 is a process explanatory view of an embodiment of themanufacturing method of the multilayered printed circuit board of thepresent invention

FIG. 8 is a cross section front view of the manufacturing apparatus of aclad metal sheet

FIG. 9 is a front view of a conventional multilayered printed circuitboard

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be concretely explained referring anembodiment shown in accompanied figures below.

At first, the structure of the multilayered printed circuit board, whichis an embodiment of the present invention, is explained referring toFIG. 7.

As shown in FIG. 7, a core of base is formed by bonding etching-stopperlayer 11, 12 (thickness: 0.5 to 3 μm) comprising nickel plating to bothsides of internal conductor layer 10 (thickness: 10 to 100 μm)comprising copper foil. Outer conductor layer 15, 16 (thickness: 10 to100 μm) comprising copper plating is formed on both sides of internalconductor layer 10 interposed by insulating layer 13, 14 comprisingresin. Base is formed by electrically connecting internal conductorlayer 10 and outer conductor layer 15, 16 with columnar conductor 17, 18(thickness: 10 to 100 μm) comprising copper. And, a multilayered printedcircuit board is formed by making patterning the surface of outerconductor layer 15, 16.

Next, the manufacturing method of the above-mentioned multilayeredprinted circuit board is explained.

First of all, nickel plated copper foil 22 is prepared by forming nickelplating 20, 21 that is to be etching-stopper layer 11, 12 on both sidesof copper foil 19 (thickness: 10 to 100 μm) that is to be internalconductor layer when the multilayered printed circuit board is completed(see FIG. 1).

Nickel plated copper foil 22 is wound around rewinding reel 23 of cladsheet manufacturing apparatus shown in FIG. 8, while copper foil 24 thatis to be columnar conductor 17 is wound around rewinding reel 25.

Nickel plated copper foil 22 and copper foil 24 are simultaneouslyunwound from rewinding reel 23, 25, parts of them are wound aroundelectrode roll 27, 28 juttingly installed in etching chamber 26, andthen they are activated by sputter-etching treatment in etching chamber26.

In this case, the activation treatment is carried out

{circle around (1)} in a hyper low pressure inert gas atmosphere of1×10⁻¹ to 1×10⁻⁴ Torr,

{circle around (2)} by glow-discharging charging alternate current of 1to 50 MHz between an electrode A consisting of nickel plated copper foil22 and copper foil 24 having contacting surface which are electricallygrounded respectively and other electrode B insulatingly held, and

{circle around (3)} by sputter-etching

{circle around (4)} in the manner that the area of the electrode exposedin plasma generated by said glow-discharging is not more than ⅓ the areaof electrode B.

After that, they are cold-press-bonded by rolling unit 30 installed invacuum chamber 29, then clad sheet for printed circuit board 31 having 3layered structure is taken up around rewinding roll 32.

Next, clad sheet for printed circuit board 31 having 3 layered structureis wound again around rewinding reel 23, while copper foil 33 that is tobe columnar conductor 18 (see FIG. 1) is wound around rewinding reel 25.Clad sheet 31 and copper foil 33 are simultaneously unwound fromrewinding reel 23, 25, respectively, parts of them are wound aroundelectrode roll 27, 28 juttingly installed in etching chamber 26, andthen they are activated by sputter-etching treatment in etching chamber26.

Also in this case, the activation treatment is carried out

{circle around (1)} in a hyper low pressure inert gas atmosphere of1×10⁻¹ to 1×10⁻⁴ Torr,

{circle around (2)} by glow-discharging charging alternate current of 1to 50 MHz between an electrode A consisting of clad sheet for printedcircuit board 31 and copper foil 33 having contacting surface which areelectrically grounded respectively and other electrode B insulatinglyheld, and

{circle around (3)} by sputter-etching

{circle around (4)} in the manner that the area of the electrode exposedin plasma generated by said glow-discharging is not more than ⅓ the areaof electrode B, and thus clad sheet for printed circuit board 34 having5 layered structure.

Further, a multilayered clad sheet formed by copper layers as top andbottom layers and interposed by nickel layer as intermediate layer inthe order of copper/nickel/copper/nickel/copper can be manufactured byrepeating press-bonding using the above-mentioned apparatus.

Moreover, a multilayered clad sheet can be manufactured by singlepress-bonding installing 3 or more of the above-mentioned rewindingreel, preparing copper foil and nickel foil on these reels andsimultaneously supplying foils from 3 or more of these rewinding reel.

Next, after clad sheet for printed circuit board 34 is cut into requiredsize, a multilayered printed circuit board is manufactured according tothe following processes explained referring FIGS. 2 to 7.

At first, after photoresist film 35, 36 are formed on copper foil 24, 33as shown in FIG. 2, they are exposed and developed.

Then, copper foil 24, 33 are selectively etched so that the portionexcept of columnar conductor 17, 18 are rejected as shown in FIG. 3.

Then, after photoresist film 37 is formed on nickel plating 20, they areexposed and developed, and further, resin 38 is coated on the surface ofnickel plating 21 so as to form insulating layer 14 as shown in FIG. 4.

Then, internal conductor layer 10 is formed by etching nickel plating20, copper foil 19, nickel plating 21 using ferric chloride or sulfuricacid added by hydrogen peroxide as shown in FIG. 5.

Then, resin 39 is coated on the surface of internal conductor layer 10so as to form insulating layer 13, and the resin surface is polished toobtain a uniform surface as shown in FIG. 6. In this case, the top ofcolumnar conductor 17 should be exposed.

Then, after the surfaces of resin 38, 39 (see FIG. 6) are roughened,outer conductor layer 16, 15 are formed on the roughened surfaces byelectroless or electrolytical copper plating. And then, outer conductorlayer 15, 16 are made patterning. Thus, the circuit is formed.

POSSIBILITY OF USE IN INVENTION

As mentioned above, in the clad sheet for printed circuit boardaccording to the present invention, the clad sheet for printed circuitboard is manufactured by press-bonding copper foil and nickel foil, orby press-bonding copper foil having nickel plating on one side or bothsides of it and other copper foil or copper foil having nickel platingon one side of it in the laminated state, so the quality of the cladsheet for printed circuit board is improved by eliminating the poregeneration which occurs when the clad sheet is trade by vaporizing andthe manufacturing cost of it can be reduced since it is manufactured bypress-bending the laminated foils. Further, since the flatness at thebonding interface can be held by controlling the stress at the bondinginterface to the low level because of press-bonding et the low reductionrate of 0.1 to 3%, and no alloy is generated at the interface becausethe heat treatment for recovering the formability is not necessary, themultilayered printed circuit board having excellent selectiveetchability can be manufactured using these clad sheets for printedcircuit board.

In the manufacturing method of a multilayered printed circuit boardaccording to another embodiment of the present invention, as a base isformed by selectively etching the above-mentioned clad sheet for printedcircuit board, the surface of it is made by patterning on the surface,and electrical connection between conductor layers is accomplished byinterposing a columnar conductor formed in said conductor layers byetching, a multilayered printed circuit board having highly integratedcircuit can be effectively and economically manufactured.

In the manufacturing method of a multilayered printed circuit boardaccording to the present invention, the clad sheet for printed circuitboard is formed by laminating a copper foil serving as a conductor layerand nickel plating serving as an etching-stopper layer and bysimultaneously press-bonding both, then the base is manufactured byselectively etching the multilayered clad sheet, and then the base iscoated by resin, plated and made patterning, and electrical connectionbetween said conductor layers is accomplished by interposing a columnarconductor formed in conductor layers by etching, and thus themultilayered printed circuit board is manufactured, so a multilayeredprinted circuit board having highly integrated circuit can beaffectively end economically manufactured.

In the manufacturing method of a multilayered printed circuit boardaccording to another embodiment of the present invention, as themultilayered clad sheet is formed by previously activation-treating thecontacting surface of copper foil and nicker plating in a vacuum chamberfollowed by laminating the copper foil and said nickel plating thancold-press-bonding both at the reduction rate of 0.1 to 3%, the flatnessat the bonding interface can be held by controlling the stress at thebonding interface to the low level and no alloy is generated at theinterface because the heat treatment for recovering the formability isnot necessary, so the multilayered printed circuit board havingexcellent selective etchability car be manufactured using thesemultilayered clad sheet.

What is claimed is:
 1. A metal clad sheet for printed circuit boardhaving a conductor layer on both outer sides of the metal sheetmanufactured by press-bonding a copper foil of which one side or bothsides have a nickel plating layer and another copper foil or a copperfoil of which one side has a nickel plating layer, wherein the copperfoil and the nickel plating layer alternate.
 2. The metal clad sheet forprinted circuit board according to claim 1 in which said metal cladsheet is a five-layered sheet comprising layers of copper foil/nickelplating layer/copper foil/nickel plating layer/copper foil.
 3. Amultilayered printed circuit board comprising: a metal base having aninternal conductor layer formed by selectively etching the outer copperfoil layer or copper foil and nickel layer of the metal clad sheet forprinted circuit board according to claim 1, an insulating layer and anouter conductor layer formed on the surface of said metal base, saidouter conductor layer being made patterning by selectively etching theouter copper foil layer or copper foil and nickel layer, and theinternal conductor layer and the outer conductor layer beingelectrically connected by interposing a columnar conductor formed insaid metal base by etching.
 4. A metal clad sheet for printed circuitboard having a conductor layer on both outer sides of the metal sheet inwhich said clad sheet is a five-layered sheet comprising layers ofcopper foil/nickel plating layer/copper foil/nickel plating layer/copperfoil.
 5. A multilayered printed circuit board having a conductor layeron both outer sides of the metal sheet comprising: a base having aninternal conductor layer formed by selectively etching the outer copperfoil layer or the copper foil and nickel layer of a clad sheet forprinted circuit board made by press-bonding copper foil and nickelplating layer an insulating layer and an outer conductor layer formed onthe surface of said metal base, said outer conductor layer being madepatterning, and the internal conductor layer and the outer conductorlayer being electrically connected by interposing a columnar conductorformed in said metal base by etching.
 6. A metal clad sheet for aprinted circuit board consisting of a conductor layer on both outersides of the metal sheet made by press-bonding a copper foil of whichone side or both sides have a nickel plating layer and another copperfoil or a copper foil of which one side has a nickel plating layer,wherein the copper foil and the nickel plating layer alternate.
 7. Ametal clad sheet for a printed circuit board consisting of afive-layered sheet comprising layer of copper foil/nickel platinglayer/copper foil/nickel plating layer/copper foil, wherein a conductorlayer is on both outer sides of the metal sheet.
 8. A multilayeredprinted circuit board consisting of a metal base having an internalconductor layer formed by selectively etching an outer copper foil layerof the copper foil and nickel layer of a metal clad sheet for a printedcircuit board made by press-bonding copper foil and nickel platinglayer; an insulating layer and an outer conductor layer formed on thesurface of the metal base; the outer conductor layer being patterned;and the internal conductor layer and the outer conductor layer beingelectrically connected by interposing a columnar conductor formed in thebase by etching; wherein the metal sheet has a conductor layer on bothouter sides of the sheet.
 9. A multilayered printed circuit boardconsisting of: a. a metal base having an internal conductor layer formedby selectively etching the outer copper foil layer or copper foil andnickel layer of the metal clad sheet for printed circuit board accordingto claim 10; b. an insulating layer and an outer conductor layer formedon the surface of the metal base, the outer conductor layer beingpatterned by selectively etching the outer copper foil layer or copperfoil and nickel, layer; and c. the internal conductor layer and theouter conductor layer being electrically connected by interposing acolumnar conductor formed in the base by etching.